This invention relates to an improved track system for tracked vehicles. More particularly, this invention relates to a tandem drive system that assures continued operation of a tracked vehicle when either main track is broken or otherwise separated.
Military land forces traditionally use mechanical mine clearing devices, such as track-width mine plows, full-width mine plows, mine rollers, mine sweepers or mine flails to support the breaching and proofing of transit lanes through a minefield or mined roadway. Due to the weight and draft forces required to push these mine clearing devices, they are also traditionally attached to the front of a main battle tank or a supporting tracked vehicle.
The breaching process usually creates a primary cleared area of a transit lane directly in front of the tracks of the host vehicle pushing the clearing devices. Currently, these track-width plows and rollers are limited in their ability to clear large areas in front of the entire vehicle. Instead, they can only provide a marginal area of clearance to either side of the width of the host tank's track width. This limitation of clearance can be hazardous to the host vehicle.
Referring to FIG. 1, a typical host vehicle 10 (a main battle tank or other tracked vehicle) is shown pushing a typical mine clearing device 12 over the ground 14 to clear a safe lane in a mined area or an area suspected of being mined. Mine clearing device 12 can be any of many different contemporary track-width mine plows, full-width mine plows, mine rollers, mine sweepers, or mine flails. Mine clearing device 12 can be pivotally mounted on host vehicle or main battle tank 10 so that it can be deployed by suitable hydraulic mechanisms at the surface 15 of ground 14 or raised up and held above it when device 12 is not needed.
Main battle tank 10 has a heavy steel, longitudinally extending main track 16 on each of its opposite lateral sides that transfers the weight of the vehicle through several roadwheels 18. Tank 10 achieves its high degree of maneuverability by mechanically engaging each main track 16 with a main drive-sprocket assembly 20 located on opposite lateral sides of and at the rear of hull 22 of tank 10 and applying or distributing the weight of tank 10 over the large surface areas of main tracks 16. FIG. 1 shows only one main track 16 longitudinally extending on one side of tank 10, it being understood that the other side of tank 10 also has a similarly disposed main track 16, roadwheels 18, and main drive-sprocket assembly 20 and other structure to be described below.
Each main track 16 is routed to extend forward on each side of tank 10 from its rear-mounted main drive sprocket assembly 20 and over a number of relatively smaller idler wheels 24. From smaller idler wheels 24 each main track 16 continues to extend to the front of hull 22 where it wraps around a larger main return-idler wheel 26 and extends downward and toward the rear of tank 10. Smaller idler wheels 24 support the weight and movement of each main track 16 between each main drive-sprocket assembly 20 and main return-idler wheel 26. More or less idler wheels 24 can be used on opposite sides of hull 22 than shown to support each main track 16.
After being routed around main return-idler wheel 26 each main track 16 extends under a series of supporting roadwheels 18 and back to each rear-mounted main drive-sprocket 22 where it is secured to itself to form a continuous, closed endless main loop 16A. Roadwheels 18 distribute the weight of the vehicle 10 to ground 14 via each main track 16 that is entrapped between roadwheels 18 and ground 14. The number and size of roadwheels 18 used to support main battle tank 10 can vary but can be as many as seven or more (per side of vehicle).
Referring also to FIG. 2, each main track 16 has equal-distantly, longitudinally spaced-apart, inwardly extending track center guide horns 30 that fit into an annular guide groove 32 in a hub 34 of each rear-mounted main drive-sprocket assembly 20. Only some of guide horns 30 are shown in FIG. 1, it being understood that guide horns 30 inwardly extend for the entire longitudinal length of each main track 16. Guide horns 30 in guide groove 32 help keep each main track 16 aligned so that gear teeth 36 of drive-sprockets 38 of each drive-sprocket assembly 20 can engage correspondingly spaced holes 40 in each main track 16 to deliver rotary power from machinery inside of tank 10. The rotary power (represented by arrow 42) is transmitted through rotated drive-sprocket assemblies 20 to tracks 16 for propulsion and maneuvering of tank 10. Each of smaller idler wheels 24, larger main return-idler wheel 26 and roadwheels 18 also has an annular guide groove (not shown) similar to each drive-sprocket assembly 20 to receive guide horns 30 and help retain each main track 16 on tank 10.
During mine clearing and mine proofing operations, mine clearing device 12 (either of or combinations of plows/sweepers/rollers) can become damaged by detonations of disrupted mines. However, irrespective of whatever clearing device is used, those lanes that have had the devices applied to them, are never considered to be 100% cleared of mines in some cases. When mine clearing device 12 is damaged, the mine detonation usually occurs at/under the first two sets of roadwheels 18 at the front 11 of tank 19 on the leading end portion of either main track 16, and usually induces separation and/or breakage of one or both of main tracks 16. This condition is usually categorized as a “mobility kill” since the crew members of the vehicle are not killed in the process but the mobility of the vehicle has been compromised. It is also of significance to note that detonations of mines occurring under tracked vehicles usually occur under their forward one-third sections since this is the portion of their tracks (and roadwheels) that first come in contact with explosive mines.
Any further movement of a track-damaged vehicle, whether forward or rearward causes the broken track to be pulled around rear-mounted main drive-sprocket assembly 20. This broken track can bunch-up and bind the vehicle's drive mechanism (drive-sprocket assemblies 20) while simultaneously causing the vehicle to steer out of the lane that was in the process of being cleared.
Often the operators of the tracked vehicles will attempt to back up and unbind the damaged track. Unfortunately, there is no force available to pull the damaged track back and it remains bunched on one side or the other around either or both main drive sprocket assemblies 20. This can cause the track-damaged vehicle to steer off-line and out of the cleared track path behind its mine clearing device 12 and expose the vehicle to further hazards of the minefield. This condition is caused by the fact that one track is broken while the unbroken track on the opposing side of the vehicle is still intact and fully functional. With only one functional track, the rearward moving vehicle will crab in a large radius path, in a direction towards the broken-track side.
When mine plows are used as mine clearing device 12, the only mines cleared can be those that are directly in front of the track-path of host vehicle 10. Following vehicles attempting to transit through this cleared lane must align their track or wheels to stay in this theoretically “cleared path”. Additionally, since some of clearing devices 12 only clear mines from the track path, anyone trying to work on a damaged-track of a disabled vehicle while it is still inside the minefield cannot approach it from the side of the vehicle since that area has not been cleared of mines. The tracks can only be approached from the rear and thus they are extremely difficult if not impossible to safely work on and repair while the host tank 10 is immobilized in the minefield. Often, the damaged host tank 10 and its attached mine clearing device 12 have to be towed out of the lane or are temporarily abandoned. In either instance, the assault lane is blocked, thus preventing the movement of any combat vehicles through the minefield.
In most cases, a second tracked mine-clearing equipped vehicle can be brought in to create a ‘safe-path’ around the incapacitated vehicle, or a new transit lane is started to support the breaching operation. However, such options can be unduly wasteful in terms of both equipment and time, can significantly degrade the efficiency of transit of military hardware and troops, and can expose them to hostile fire by an adversary.
Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for a track system having a tandem drive that assures continued operation of a tracked vehicle when the main track is broken or otherwise separated to provide the ability to maneuver in a mined area.